Hydrological Seasonality Drives DOM-Bacteria Interactions in the Rushan River Basin.

Area of Science:

• Environmental Chemistry
• Microbiology
• Ecology

Background:

• Dissolved organic matter (DOM) is crucial for riverine ecosystem function.
• Understanding DOM-microbe interactions is key to riverine health.
• Hydrological controls on these interactions remain understudied.

Purpose of the Study:

• To investigate the impact of hydrological seasonality on DOM characteristics and microbial communities in the Rushan River Basin.
• To elucidate the relationships between DOM dynamics and microbial assembly.
• To identify pathways regulating DOM transformation by microorganisms.

Main Methods:

• Integrated 3D excitation-emission matrix spectroscopy (3D-EEMs) and parallel factor analysis (PARAFAC) for DOM characterization.
• Employed 16S rRNA sequencing for microbial community analysis.
• Utilized structural equation modeling (SEM) to quantify microbial regulation pathways.

Main Results:

• PARAFAC identified distinct DOM signatures between dry and wet seasons, with protein-like and humic-like components varying significantly.
• Dry-season DOM was rich in tyrosine-like substances, while wet-season DOM showed elevated tryptophan-like and terrestrial fulvic acid components.
• Microbial communities differed seasonally, with higher alpha-diversity in the wet season, dominated by Proteobacteria and Actinobacteriota, versus Bacteroidota and Verrucomicrobiota in the dry season.

Conclusions:

• Hydrological seasonality synergistically regulates DOM composition and microbial structure in river ecosystems.
• Microorganisms play a role in protein degradation and humification processes.
• Findings provide insights for adaptive water quality management strategies.